1. Field of the Invention
The present invention relates to an image reading apparatus for reading image information of an original resting on an original resting portion and, in particular, to an image reading apparatus to be used in an image scanner, a facsimile apparatus or the like. Further, the present invention relates to an image reading apparatus to be used in an image forming apparatus, such as a copying machine, for forming images by the electrophotographic system, electrostatic recording system, etc.
2. Related Background Art
Conventionally, Japanese Patent Application Laid-Open No. 61-149920 and Japanese Patent Application Laid-Open No. 9-270895 propose apparatuses which perform scanning while holding a contact image sensor serving as the image reading means in contact with the back surface of an original glass stand serving as the light transmitting member.
These publications disclose typical examples of the technique for scanning an image by a contact image sensor, providing a description of a connection cable for exchanging signals between the contact image sensor and an image processing portion serving as the image processing means. In Japanese Patent Application Laid-Open No. 9-270895, a flat cable is adopted as the connection cable.
FIG. 10 shows the construction of a conventional apparatus. Reference Numeral 109 designates an image reading apparatus, reference numeral 110 designates an original glass stand, and reference numeral 101 designates a contact image sensor which has a width smaller than that of the original glass stand 110 and which includes a halogen lamp 111 as the light source. Reference numeral 102 designates an inverter board for controlling the halogen lamp; a DA converter is mounted thereon.
Reference numeral 103 designates a flat cable for supplying a digital image signal output from the inverter board and a signal from the halogen lamp to a main-body side control board serving as the image processing portion (not shown).
Reference numeral 104 designates a carriage for supporting the contact image sensor 101 while holding it in close contact with the back surface of the original glass stand 110. The carriage 104 and the contact image sensor 101 constitute an image reading unit.
Reference numeral 106 designates a stepping motor. The carriage 104 is reciprocated in the sub-scanning direction along a guide shaft 107 by a timing belt 105. Reference numeral 108 designates a backup pulley for securing the timing belt 105 in position with a predetermined tension.
The width of the contact image sensor 101 is somewhat larger than a width of the maximum original to be read. The connector portion thereof, to which the flat cable 103 is connected, is usually arranged within the original readable range.
In the case of the apparatus construction shown in FIG. 10, when the connecting portion of the flat cable is connected to the connector portion, reciprocation of the image reading unit in the sub-scanning direction causes the flat cable 103 to be bent below the original glass stand 110.
At this time, as shown in FIG. 11, the flat surface of the flat cable 103 moves while in contact with the back surface of the original glass stand 110.
When this image reading apparatus is left to stand for a long period of time in an ordinary installation place, such as an office, a very small quantity of dust in the air may be attracted by static electricity generated on the surface of the flat cable 103, thereby blackening the surface of the flat cable 103 after a while.
And, the entire flat portion of the blackened flat cable 103 may come into contact with the back surface of the original glass stand 110, thereby soiling the back surface of the original glass stand 110. When the back surface of the original glass stand 110 is soiled, the stain on the back surface of the original glass stand 110 will also be read when image reading is performed, resulting in defective image reading.
It might be possible to cause the flat cable 103 to inflect outside the image readable region. In that case, however, it is necessary that there should be no protrusions such as screws in the inflecting range of the flat cable 103. Further, it is necessary to additionally provide a movement range for the flat cable 103 outside the movement range for the contact image sensor 101, resulting in an increase in apparatus size.